Treatment of wells



- carbon tetrachloride and gasoline.

Patented Oct. 5, 1943 TREATMENT OF WELLS Francis N. Alquist, Midland, Mich., assignor to The Dow Chemical Company, Midland, Mich., a corporation of Michigan No Drawing. Application August 15, 1939, Serial No. 290,257

2 Claims.

This invention relates to a method or facilitating the production of deeps wells such as oil and gas wells. Specifically the invention is concerned with a method of increasing the output of wells in which the pay formation, tubing, or

other parts of the well have become clogged by deposits of waxy asphaltic materials known as paramn.

It is a well-known fact that the production of wells producing oil or gas declines. In some instances this decline is rather gradual, while in others the production may fall oiT rapidly although the supply of oil contained in the producing formation is not nearly exhausted. In many cases the decline in the rate at which oil and/or gas can be obtained from a well is due to the deposition of clog n deposits of waxy asphaltic materials known as paraffin in the pay formation, well tubing, and other locations in the well.

Various methods have been proposed for removing these clogging deposits so as to facilitate or increase the output of the well. For example, the use of solvents has been proposed. Among the solvents that have been proposed for use are However, while the above solvents are the only ones that have met withany degree of success for the purpose of removing paraffin deposits, their use is accompanied by disadvantages that render them unsatisfactory in many instances. As an illustration, carbon tetrachloride i a very satisfacto y solvent from the viewpoint of its disintegrating action on paraffin, but due to the fact that it breaks down into highly corrosive end products as it is being subjected to cracking along with the oil, serious damage to the refinery apparatus generally results. The use of gasoline is also highly unsatisfactory due to the fact that its composition varies so widely that it is impossible to pre-. dict whether a particular gasoline will be satisfactory as regards its ability to clean parafiln from a well without actually employing the particular gasoline in question. In addition, large quantities of gasoline are usually necessary to effectively clean a well or paraflln.

It is, therefore, an object or th invention to provide a highly efiective paraflln solvent which is entirely unaffected as regards breaking down.

into corrosive end products when it is subjected to refinery processes.

It is also an object of the invention to provide a method whereby the clogging deposits of paraffln may be removed from the well and the pro- .later finds its way into the oil refinery where it duction of the well facilitated by the use of com paratively small volumes of a solvent.

Another object of the invention is to provide a paraflin solvent of definite and unchanging composition.

Still further objects and advantages of the invention will become apparent as the description of .the invention proceeds.

I have discovered that by bringing a relatively small quantity of a solvent consisting substantially of cyclohexane into contact with the parafiin deposited in oil wells, the paraflin deposited therein is disintegrated so that itcan be readily removed from the well and greatly increased .production can be obtained therefrom, and, in addition, refinery corrosion due to the solvent breakins down in the cracking stills of the refinery is entirely eliminated.

The invention then consists of the method hereinafter fully described and particularly pointed out in the claims.

The manner of bringing my improved solvent into contact with the paraffin deposited in the oil well varies according to'the tyne of the well and the location of the deposit torbe removed. In carrying out the invention in a well equipped with the usual casing and tubing wherein'the paraflin is deposited on th face of the pay for.- mation, any fluid standing in the well is preferably first removed, although some dilution with the well fluids does not prevent the cyclohexane from bringing about the disintegration or solution of the paraffln. The cyclohexane is then preferably introduced into the well through the casing and circulated up through the tubing, as by pumping, and thereafter led back into the casing through suitable connections between the tubing and the casing to secure a washing effect on the face of the pay. After such circulation has been carried out for a period-of time, the well may be pumped out and the disintegrated paraffin and treating agent thus be removed from the well. Thereafter. the well may be put back into production.

Various other methods of employing my treat ing agent may be used, depending upon the location of the deposit to be treated. For example, if

paraflln is deposited in the upper portion of the tubing so as to completely flllthe tubing, the cyclohexane may be introduced into the tubing and allowed to stand for a period of time, after v vary quite widely depending on the extent of the formation to be treated or the amount of deposit in the tubing or other location. In general, from 2 to 50 gallons or more may be suitably employed. The treating agent should be allowed to remain in contact with the formation for a suitable length of time. For example, where the treating agent is circulated down the casing and up the tubing, from l'to 12 hours or more, preferably from 3 to 10, may be required. If the cyclohexane is allowed to stand in the casing in contact with the deposit from '7 to 10 hours or more, generally satisfactory results are produced.

I If desired, the cyclohexane may be mixed with other well-known paramn solvents. For example, mixtures of cyclohexane and benzene are highly effective. The amount of benzene to include in the solrvent mixture which gives highly satisfactory results is from 10 to 50 per cent or more by volume.

Employing the foregoing improved solvent, highly improved results are obtained as regards facilitating the production from wells having deposited therein clogging deposits of parafiin or the like, and at the same time danger due to the solvent later breaking down in the refinery to corrosive end products is entirely eliminated.

Other modes of applying the principle of my invention may be employed instead of those explained, change being made as regards the method herein disclosed, provided the step stated by any of the following s or the equivalent of such stated step be em oyed.

I therefore particularly point out and distinctly claim as my invention:"

1. In a method of treating a well to remove deposits of paraflin and facilitate th production therefrom, the step which consists in introducing into the well bore a solvent mixture comprising upwards of 50 per cent of cyclohexane by volume, the balance being a solvent of parafiin.

2. In a method of treating a well to remove a deposit of paramn and facilitate the production therefrom, the step which consists in introducing into the well bore a solvent mixture comprising 10 to 50 per cent of benzene, the balance being cyclohexane.

FRANCIS N. ALQUIST. 

